1. Field of the Invention
The present invention relates to a sheet processing apparatus which processes a sheet and an image forming apparatus equipped with the sheet processing apparatus. In particular, the invention relates to a sheet processing apparatus which can receive and put the next sheet on standby while processing a sheet, and an image forming apparatus equipped with the sheet processing apparatus.
2. Related Background Art
Conventionally, as image forming apparatuses, for example, there are a printer which prints digital information using an electrophotographic technique, and a multifunction printer installing an image reading apparatus together with the printer as a base, thereby being given a multifunction. Some of those printers have a sheet processing apparatus which processes a sheet having an image formed thereon.
Some conventional sheet processing apparatuses have such functions of stacking a sheet discharged from a printer on a sheet stacking portion, performing, for example, stapling process to the sheet, and discharging the sheet thereafter (see Japanese Patent Application Laid-Open No. 2002-80162).
However, the conventional sheet processing apparatus cannot receive a sheet in the next job until the sheet processing apparatus discharges a sheet bundle after starting the stapling process. Therefore, the conventional sheet processing apparatus has a problem in that sheet processing efficiency is lowered in proportion to the number of sheets which cannot be received.
In addition, an image forming apparatus having such a sheet processing apparatus has to bring a printer engine to a standstill state until the sheet processing apparatus receives a sheet. Therefore, the conventional image forming apparatus has a problem in that sheet processing efficiency is low because the image forming apparatus cannot form images on sheets successively.